Accumulated Other Comprehensive Income (Loss) (AOCI balances) (Details 2) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
As of	$ 2,999,536	$ 2,916,782	$ 2,884,388	$ 2,915,145	$ 2,916,782	$ 2,915,145
Other Comprehensive Loss, Net of Tax	(12,095)	8,290	(33,221)	10,812	(3,805)	(22,409)
As of	3,038,854	2,999,536	2,876,864	$ 2,884,388	3,038,854	2,876,864
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
As of		203,829			203,829
Other comprehensive loss before reclassifications					(1,297)
Net amount reclassified from accumulated other comprehensive income (loss)					(2,508)
Other Comprehensive Loss, Net of Tax					(3,805)
As of	200,024				200,024
Cumulative Foreign Currency Translation Adjustment [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
As of		(29,270)			(29,270)
Other comprehensive loss before reclassifications					(1,071)
Net amount reclassified from accumulated other comprehensive income (loss)					0
Other Comprehensive Loss, Net of Tax	(11,104)		(31,167)		(1,071)	(19,603)
As of	(30,341)				(30,341)
Unrealized Gain on Pensions and Other Postretirement Plans [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
As of		232,836			232,836
Other comprehensive loss before reclassifications					0
Net amount reclassified from accumulated other comprehensive income (loss)	(1,026)		(2,355)		(2,410)	(3,298)
Other Comprehensive Loss, Net of Tax	(1,026)		(2,355)		(2,410)	(3,298)
As of	230,426				230,426
Cash Flow Hedges [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
As of		$ 263			263
Other comprehensive loss before reclassifications					(226)
Net amount reclassified from accumulated other comprehensive income (loss)					(98)
Other Comprehensive Loss, Net of Tax	35		$ 301		(324)	$ 492
As of	$ (61)				$ (61)